Anthropic Claude Sonnet 5.5 and Claude Opus 5.5 are now available on Kiro in AWS GovCloud (US)

<p>Two new Anthropic models are now available in the Kiro IDE and CLI for the AWS GovCloud (US) Regions.</p> <p>Claude Opus 5.5 is Anthropic's most capable Opus model yet and a step up from Opus 5 on long-running agentic coding work. Opus 5.5 thinks adaptively on every request, deciding how much effort each task needs, and completes tasks with roughly 40% fewer tool calls and about half the tokens of Opus 5 in Kiro's internal benchmarking. Available with a 1M context window and 2.0x credit multiplier, down from Opus 5's 2.2x.</p> <p>Claude Sonnet 5.5 is Anthropic's fastest Sonnet model to date and a natural upgrade for teams already building on Sonnet 5. Output is more than 30% faster, real-world coding and knowledge work approaches Opus 5.5 performance, and clearer writing makes it a stronger collaborator, giving developers a cost-performance dial between maximum capability and higher throughput. Available with a 1M context window and 1.3x credit multiplier.</p> <p>Ensure your IDE or CLI is updated to the latest version, then restart it to access the new models from the model selector. For more details, visit the <a href="https://docs.aws.amazon.com/govcloud-us/latest/UserGuide/govcloud-kiro.html">GovCloud documentation</a>, the <a href="https://kiro.dev/docs/enterprise/monitor-and-track/">monitoring and tracking guide</a>, or contact your AWS account team. To learn more about Kiro, visit the <a href="https://kiro.dev/">Kiro product page</a>.</p>